Skin Substitutes as Treatment For Burn İnjuries

Abstract

Over the last decades the mortality of severely burned patients decreased significantly. This is due to major achievements in burn surgery such as early resuscitation, improved respiratory management of inhalation injury, better control of infection, modulation of the hypermetabolic response after trauma, and to a vast amount the introduction of early burn wound excision and grafting. Early burn wound excision has been shown to have several benefits in severely burned patients, such as decreased operative blood loss, decreased length of hospital stay, fewer septic complications, and decreased mortality in non-elderly adult burned patients. But especially severely burned patients lack the skin donor sites necessary to achieve definite burn wound coverage by autografting. As conventional meshing procedures of autograft skin only can provide 4:1 (Tanner/ Brennan mesher) up to 9:1 (modified Meek technique) expansion of the skin graft definite coverage of excised burn wound remains problematic. The approach using cultured epidermal autograft (CEA) sheets (Epicel™ - Genzyme Tissue Repair Corporation) with or without an additional dermal layer (Integra™ - Integra Life Sciences/ Johnson&Johnson, Alloderm™ -Life Cell Corporation) is promising. However the excised wound requires additional temporary cover for about 3 weeks until the keratinocytes harvested at admission are grown to large enough sheet grafts to obtain full coverage of the wounds. Currently, the inferior long term durability and the increased fragility of CEA leads to a significant amount of graft failure and an increased need for re-grafting procedures A new product (FDA approval for chronic venous ulcer wound) Apligraf™ - Organogenesis/Novartis was introduced to avoid the waiting period until CEA are available. It is a “shelf product” manufactured from human male foreskin tissue consisting of an epidermal keratinocyte layer and a dermal layer of fibroblasts in a bovine collagen matrix. It can be applied immediately and is gradually replaced by the ingrowth of autologous skin cells. At current time it has been used in chronic venous ulcers and partial thickness wounds. As for temporary coverage all new technologies have to compare to the gold standard of homograft or xenograft (pig skin) coverage. TransCyte™ - Smith&Nephew, and Dermagraft® are other bioengineered “shelf products” consisting of human neonatal foreskin fibroblasts which are integrated in a synthetic epidermal layer (siliconepolymer). It can be applied immediately after excision but requires removal and second stage autografting for definite wound coverage Its use in partial thickness burns is promising, but in our view other more cost-effective dressing materials, which yield basically the same results (Biobrane™ - Bertek, Hydrocolloids as Duoderm™ - Convatec, or occlusive dressing as Opsite™) should be preferred. The major issues to be addressed in the future of tissue-engineered skin are delay in definite permanent coverage, the improvement of long term results regarding durability, fragility of the epidermal surface, and scar formation, as well as the enormous financial costs. In conjunction with gene therapy, it may become possible to differentially stimulate autologous cells in tissue engineered skin constructs and eventually achieve a permanent esthetically and functionally optimal restoration of skin integrity